Blowers



' July so, 1957 J. R. THYGESON BLOWERS File l Aug. 11., 1954 'iinrtetates batent 2,801,642 Patented July 30, 1957 Free BLOWERS John R.Thygeson, Abington Township, Pa., assignor to Proctor & Schwartz, Inc,Philadelphia, Pa, a corporation of Pennsylvania Application August 11,1954, Serial No. 449,181

7 Ciairns. (Cl. 230-114) The present invention relates to centrifugalblowers and has particular application to blowers of this type fordirecting air against or through material in a drying chamher. Thisapplication is a continuation-in-part of the application filed May 25,1953, Serial No. 357,126, now abandoned, entitled Improvements inBlowers.

Prior to the present invention, centrifugal blowers have conventionallybeen of the scroll type. The conventional scroll-type blowers, however,have not been entirely satisfactory for drying chambers since the blowerexhausts a column of air in which the pressure varies substantiallyacross the column. This variable pressure is not predeterminable sinceit is not regular and since the high pressure zones in the air columnshift laterally as the impeller speed is changed. As a result, the aircolumn does not dry the material in the chamber uniformly, the materialin the high pressure and velocity zones being dried more rapidly thanthe material in the low pressure zones. Therefore, it is necessary toretain the material in the chamber until that portion exposed to the lowpressure zone is completely dried, and frequently the remaining portionof the material becomes overdried and damaged.

in order to partially compensate for the varying pressure in the columnof air exhausted by the blower, it has been customary to provide bafliesfor directing the air onto the material to be dried. This method ofcompensation is not completely satisfactory since the positioning of thebafiies is efiective for only one rotary speed of the blower impellerand to locate the bafiies properly, it is necessary to run a series oftests to determine the exact pressure and velocity distribution acrossthe mouth of the blower. In addition, the prior blowers do not operateat maximum efiiciency because there is a certain amount of leakage ofair from the high pressure side of the impeller into the low pressureintake thereof. As a result of this leakage there is a circulation ofair about the blower impeller which may also contribute to the varyingpressure across the mouth of the blower.

With the foregoing in mind, a principal object of the present inventionis to provide a blower which has a uniform pressure distribution acrossits mouth.

A further object of the invention is to provide increased efliciencythrough the reduction of friction and leakage losses.

Another object of the invention is to provide a blower constructionwhich eliminates the requirement for specially constructed scrollcasings.

Still another object is to provide a blower having a simple adjustmentto provide optimum efiiciency upon regulation of the impeller speed.

A still further object is to provide a novel blower for drying chambersand the like having two diametrically opposed outlet orifices and asingle impeller for discharging the drying medium through said orifices.

These and other objects of the invention and the various features anddetails of the construction and operation thereof are more fully setforth hereinafter with reference to the accompanying drawing in which:

Fig. 1 is a side elevational view of a blower as seen from the suctionside thereof with a portion of the casing broken away to illustrate theoperation of the device;

Fig. 2 is a vertical sectional view taken on the line 2-2 of Fig. 1, and

Fig. 3 is a side elevational view of a modified form of blower havingits side cover plate removed.

The present invention contemplates a blower which provides a uniformdistribution of pressure across its outlet opening. The casingsurrounding the rotary impeller is generally rectangular and is providedwith a cut-off plate projecting into close proximity to the outerperipheral surface of the impeller. Rotation of the impeller causes apredetermined airflow within the casing which assumes a scroll-like pathstarting at a point adjacent the cut-off plate and gradually increasingin width until it extends laterally across the outlet opening. The airpressure across the opening is constant and, therefore, expels a columnof air having uniform pressure and velocity across itswidth.

Referring more particularly to the drawing, the blower illustrated inFigs. 1 and 2 comprises a narrow rectangular casing 11 defining arectangular air chamber closed on the bottom and all four sides andhaving an open upper end 12 therein which provides an outlet opening inthe casing. Mounted adjacent the lower corner of the casing andextending substantially between the opposite side walls thereof is astandard axial-inlet, radial-exhaust vane type impeller 13 which drawsair axially through an inwardly flared opening 14 in the side wall ofthe casing and forces the air radially outward into the interior of thecasing. The impeller is rotatably mounted on the side wall of the casingopposite to the flared inlet opening 14 and is driven, for example, bymeans of an electric motor 15.

The impeller 13 is of conventional construction comprising opposedradial walls 16 and 17 having mounted therebetween a plurality of vanes18 for expelling the air into the interior of the casing 11. The forwardradial wall 17 of the impeller is annular in form and the innerperipheral surface thereof defines the eye 19 of the impeller whichconstitutes the axial inlet thereof. The eye 19 corresponds in size tothe inwardly flared opening 14, and is positioned in axial alignmenttherewith to provide an unimpeded air inlet for the blower. It should benoted that the forward wall of the impeller is closely adjacent thestationary inlet opening 14 so as to reduce to a minimum the clearancewhich permits air leakage into the inlet opening from the interior ofthe chamber defined by the casing. V

In accordance with the present invention, the direction of the flow ofair in the casing is controlled to provide an equal air pressure andvelocity distribution across the length and the width of the casingoutlet opening 12. To this end, a cutoff plate 21 is mounted adjacentone side of the casing outlet opening 12 for pivotal movement about anaxis parallel to the axis of the impeller13. The cut-off plate ismounted on a shaft 22 which is journaled between the side walls of thecasing in the junction between the open upper end 12 and the adjacentend wall of the casing 11. The cut-off plate 21 depends down wardly andinwardly into close proximity with the outer peripheral surface of theimpeller 13 in a generally radial direction thereto, and extendslaterally the full width of the casing, and is exposed to air in saidchamber at both sides of said plate.

Means is provided to adjust the position of the plate 21, and to thisend, a crank 23 is keyed to the shaft 22 and mounts a plunger 24operable to engage in one of a series of detents 25 on the forward wallof the casing. The cut-ofi plate 21 is adjustable to obtain optimum ef-'3 accordance with the rotary speed of the impeller, and the detents 25"are positioned in accordance with the various rotary speeds of themotor 15. AMThe .operation of the impellerB-discharges theair underpressure into the interior of the casing 11 where it is expelled throughthe outlet opening 12 in a column -having uniform .pressureand velocitydistribution across its width. The air flow in the casing follows ascroll- .like path starting from a point adjacent the junction of oneside of the cut-off plate and the impeller and gradually increasing inwidth until it extends entirely across the outlet opening 12 where it isdischarged. This scrolllike path is determined by the pressure of'theair within.

.the casing which builds up a cushion of air about the interior walls ofthe casing in accordance with the most efiicient path for the air flow.Since the path is determined primarily by the air pressures and onlysecondarily -by the'-walls1of the casing, there is relatively lowfriction loss between the air current and the stationary walls. ,Iheefficiencyl of the blower is, therefore, substantially increased. "The,airpressure built up adjacent the other 'side o'f the cut-off plate 21when the plate is properly .pOtitiOned prOVidesaunifrom pressure andvelocity'distribution"acrossithewidth of the opening 12. Since the pathof the air flow and the pressures in the casing change .in. accordancewith the rotary speed of the impeller, it is -desirable to adjust thecut-offplate 21'to compensate for the changes to provideoptimumefiiciency. If desired, :the, detents 25 may be calibrated tocorrespond with given rotary speeds of the'motor so as to provide simpleadjustment ofthe cut-off plate upon regulation of the -rotary speed ofthe impeller. V

Tofurthefiincrease the efliciency of the blower, circulationfof the'airfrom the pressure zone interiorly of the casing in the suction zone inthe inlet opening of the impeller is prevented by providing a pluralityof auxiliary blades 26 spaced circumferentially about the forwardannular wall 17 of the impeller. The blades 26 project axially beyondthe forward wall of the impeller and'surround the inwardly flaredopening 14. These 'blades effect apressure drop adjacent their inneredges and effectively" preclude leakage of air. through the clear-'Vance between'the forward wall not the impeller and the inlet opening14. A modified form of the invention is shown in Fig. 3

'wherein a casing 31 forms a rectangular air chamber having its oppositeside walls 32, 32 open for 'thedis- "charge of a column of air. In thisform of the invention,

' an impeller 33 similar in detail to the impeller 13 is providedintermediate the end walls of the casing 31. A motor (not shown) drivesthe impeller to effect the discharge of the air from the casing. As inthe previously described embodiment, the-front side wall which isremoved in Fig. 3 is provided withaflar edopening similar to the opening14. A a

Inthis embodiment of the invention, two cut-0E plates 35, 35 areprovided at diagonally opposite corners of the casing. 'Each plate ismounted on a shaft 36 and is journaled in the casing 31 at the junctionof the open side wall 32 and the end wall. A crank (not shown) isprovided to adjust the angularity of each cut-ofi plate 35. As in theprevious embodiment, the angular position of the cut-off plate maybecalibrated in accordance with the rotary speeds of the impeller toprovidegoptimum efficiency of the blower.

This form of the invention operates similarly to the above-describedembodiment so as to discharge a column of air from the open side 32having uniform pressure distribution across its width- The' inventioneliminates the necessity for a scroll-type casing and ai fords the useof a simple rectangular box-like structure. Thus, the cost of the bloweris substantially. reduced while maintaining'optimum efiiciency. 7

From the foregoing description, it is seen that the present inventionprovides a blower simplein construe across its outlet opening, and inwhich the'losses due to friction and leakage have: been substantiallyeliminated.

While particular embodiments of the invention have been hereinillustrated and described, it is not intended to limit the invention tosuch disclosures, and changes and modifications maybe made therein andthereto with in the scope of the following claims.

I claim: I e

l. A centrifugal blower comprising a generally rectangular casing havingone side open for exhausting a column of air, a vane-type impellerhaving a central eye and mounted for rotationin said casing about anaxis substantially parallel to said open side'and adjacent one end wallof the casing, means in said casing defining inwardly-flared walls of anair inlet aperture in registry with the eye of said impeller, aplurality of generally axially disposed blades spaced circumferentiallyabout proximity to'said impeller whereby upon rotation of said'impellera column of airis exhausted from the'eye' of, theimpeller through saidopen side.

2. A centrifugal blower comprising a generally rec- ;tangular casinghaving opposite sides open from exhausting columns of air, a vane-typeimpeller having a central eye and mounted for rotation in said casingabout an axis substantially parallel to said open sides and adjacentopposite end. walls of the casing, means in said casingdefining'inWardly-fiared walls of an air inlet aperture in registerywith the eye of said impeller, a plurality of generally axially disposedblades spaced circumferentially about said impeller, and projectingaxially so as to sur- 7 round said inwardly flared walls, said bladesbeing operable upon rotation of said impeller to reduce the pres-.

sure within said casing at the opposite side of said flared walls fromsaid inlet opening, and cut-off plates, one extending substantially fromthe angle between one open side and one end wall of the casing andterminating in close proximity to said impeller and the other extendingsubstantially from theangle between the opposite open side and theOpposite end wall and terminating in close proximity to said impellerwhereby upon rotation of said impeller columns of air having a uniformpressure distribution across their width are exhausted from the eye ofthe impeller through said open sides.

3. .A centrifugal blower comprising a casing forming a generallyrectangular air chamber having one side open for exhausting a column ofair, a vane-type impeller having a central eye, said impeller beingmounted for rotation in said casing about an axis substantially parallelto said open side and adjacent one end wall of the casing, meansdefining an air inlet to the eye of said impeller, and a cut-oil plateextending substantially from the junction between said open side andsaid one end wall of the casing and terminating in close proximity tosaid impeller and being exposed to air in said chamber on both sides ofsaid plate whereby upon rotation of said impeller, the vanes of saidimpeller exhaust a column of air from the eye of the impeller outwardlythrough said open side; j

4. A centrifugal blower comprising a generally're'ctangular casinghaving opposite sides open for exhausting a column of air, a vane-typeimpeller having a central eye, said impeller being mounted for rotationin said casing .about anaxis substantially .parallel to said open sidesand adjacent opposite end walls of the casing, means defining an airinlet to the eye of said impeller, a cut-ofi plate extendingsubstantially'from the junction between one open side and one end wallof the casing and terminating in close proximity to said impeller and asecond cut-01f plate extending substantially from the junction betweenthe opposite open side and the opposite end wall of the casing andterminating in close proximity to the impeller, whereby upon rotation ofsaid impeller columns of air having a uniform pressure distributionacross their width are exhausted from the eye of the impeller throughsaid open sides.

5. A centrifugal blower comprising a generally rectangular casing havingone side open for exhausting a column of air, a vane-type impellerhaving a central eye, said impeller being mounted for rotation in saidcasing about an axis substantially parallel to said open side andadjacent one end wall of the casing, means defining an air inlet to theeye of said impeller, an adjustable cutotf plate extending substantiallyfrom the junction between said open side and said one end wall of thecasing and terminating in close proximity to said impeller whereby uponrotation of said impeller a column of air having uniform pressuredistribution across its width is exhausted from the eye of the impellerthrough said open side, and means to adjust the angular position of saidcut-ofi plate in the junction between said open side and said one endwall.

6. A centrifugal blower comprising a generally rectangular casing havingone side open for exhausting a column of air, a vane-type impellerhaving a central eye, said impeller being mounted for rotation in saidcasing about an axis substantially parallel to said open side andadjacent one end Wall of the casing, means defining an air inlet to theeye of said impeller, a shaft journaled in the casing in parallelismwith the axis of said impeller in the junction between said open sideand said one end wall of the casing, an adjustable cut-ofi plate mountedon said shaft and extending and terminating in close proximity to saidimpeller whereby upon rotation of said impeller a column of air having auniform pressure distribution across its width is exhausted from the eyeof the impeller through said open side, and means to adjust the angularposition of said shaft comprising a handle keyed to said shaft, meansdefining a plurality of detents in said casing, and a plunger mounted onsaid handle and operative to selectively engage said detents to therebypositively position said cut-ofi plate angularly relative to saidimpeller.

7. A centrifugal blower comprising a generally rectangular casing havingone side open for exhausting a column of air, a vane-type impellerhaving a central eye, said impeller being mounted for rotation in saidcasing about an axis substantially parallel to said open side, drivemeans for rotating said impeller, means defining an air inlet to the eyeof said impeller, and a cut-off plate extending substantially from thejunction between said open side and one end wall of the casing andterminating in close proximity to said impeller substantially radialthereto whereby upon rotation of said impeller a column of air isexhausted from the eye of the impeller through said open side, and meansfor adjusting the angular position of said cut-off plate from saidjunction in accordance with the rotary speed of said drive means.

References Cited in the file of this patent UNETED STATES PATENTS783,267 Harris Feb. 21, 1905 2,212,050 Samuelson et al Aug. 20, 19402,252,064 Cornell Aug. 12, 1941 2,330,938 Williams Oct. 5, 19432,537,523 Frost Jan. 9, 1951 2,634,806 Hirtz Apr. 14, 1953 2,674,811Thornburg Apr. 13, 1954

